Snow Water Equivalent & Precipitation - March monthly precipitation in the Great Basin was 106% of average. After a very warm 2 weeks during mid March that brought on early melt, a series of wet storms brought snow totals back to 100% of average. Indexed snow totals are now 100% of average in the Weber and Ogden basins, 99% in the Provo basin, 95% in the Bear River basin and 108% in the Six Creeks basin. Seasonal precipitation for the Great Basin Salt Lake Basin is now 104% of average and overall indexed snow water equivalents are 97% of average for all 4 basins.

Soil Moisture & Streamflow - Modeled soil moisture heading into the winter was much below average in all headwater regions, which tends to lower April through July volume forecasts. However, some early runoff has streamflow for selected points in each of the four main drainages 103% of average.

Short Term Precipitation Forecasts - Weather guidance from National Weather Service Meteorological Models show cool and wet conditions during the first 6-10 days of April. Short term CPC guidance shows no signal for the second half of April.

General Discussion - Longer range predictions from NOAA's Climate Prediction Center are now factoring in a weak La Nina episode, predicted to last through the spring of 2009. Please reference the web link above for further details and effects within the Great Basin.

Volumetric forecasts were raised due to increases in snow water equivalents on the Weber, Provo and Bear and held mostly steady for Utah Lake and it's associated drainages. Last month we began forecasting the max summer elevation of the Great Basin. Current ESP estimates are for a final maximum elevation of 4194.66 ft.above mean sea level by early to mid May, 2009. The lake is currently at 4194.13 ft. above mean sea level

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Bear River drainage improved during March. Monthly precipitation was 115% of average and snow water equivalent increased to 95% of average. Seasonal precipitation is currently 104% of average.

Soil Moisture & Streamflow - Observed streamflows for March were estimated for Bear at the UT/WY State line at 45% of average. Observed flows on the Logan River nr Logan above State Dam were 84% of average.

Short Term Precipitation Forecasts - Short term National Weather Service Models are indicating a period of cool and wet weather during the first 6-10 days of April. Short term CPC guidance shows no signal for the second half of April.

General Discussion - Volumetric forecast for April through July range from 53% at Bear River nr Montpelier to 93% of average at the Bear River, Utah, Wyoming State line.

Snow Water Equivalent and Precipitation - Conditions in the Weber and Ogden River River basins improved after a warm and dry period in mid March. Monthly precipiation totalled 114% of average, while snow water equivalent numbers improved to 100% of average. Seasonal precipitation increased slightly to 101% of average.

Soil Moisture & Streamflow - Soil moisture conditions were dry in the upper basin prior to winter snow accumulation, varying from 70% to 89% of average. Observed streamflows this month for Weber at Oakley were 50% of average and Chalk Creek at Coalville were 70% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period cool and wet weather during the first 6-10 days of April. Short term CPC guidance shows no signal for the second half of April.

General Discussion - Volumetric forecasts now range from 85% at Weber River at Echo Reservoir to 102% of average at Wheeler Creek near Pineview Reservoir.

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Six Creeks basins improved during March. Monthly precipitation was 133% of average and snow water equivalent is 108% of average. Seasonal precipitation now totals 113% of average.

Soil Moisture & Streamflow - Streamflows in Mill Creek 60% of average. Soil moisture in the fall ranged from 50%-90% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period of cool and wet weather during the next 6-10 days of April. Short term CPC guidance shows no signal for the second half of April.

General Discussion - Volumetric forecasts were raised slightly this month. Forecast now range from 93% at Emigration Creek near Salt Lake City to 105% at City Creek near Salt Lake City.

Snow Water Equivalent & Precipitation - Snow Water Equivalent and precipitation conditions in the Utah Lake drainages improved slightly during the later half of March . Monthly precipitation totalled 96% and snow water equivalent numbers are 99% of average. Seasonal precipitation now totals 101% of average.

Soil Moisture & Streamflow - Streamflows for the Provo River at Woodland were 85% of average. Soil moisture in the fall along the Provo River range from 50-90% of average. The Spanish Fork drainage fall soil moisture ranges from 70% to 99% of average.

Short Term Precipitation Forecasts - Short term weather service models are indicating a period of cool and wet weather during the first 6-10 days of April. Short term CPC guidance shows no signal for the second half of April.

General Discussion - Volumetric forecast for Utah Lake drainages were mostly unchanged this month. The forecast now range from 86% at Utah Lake to 91% at Spanish Fork River Nr Castilla.

Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).

10% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 10% chance of being exceeded. Previously referred to as "Reasonable Maximum Forecast".

50% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 50% chance of being exceeded. Previously referred to as "Most Probable Forecast".

90% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 90% chance of being exceeded. Previously referred to as "Reasonable Minimum Forecast".

Acre-Foot (af): The volume equal to one acre covered one foot deep (43,560 cubic feet). See kaf below.

Average: The arithmetic mean. The sum of the values divided by the number of values. Values from 1971-2000 are used for this publication.

Categories: Much Above Average=Greater than 130%, Above Average=111-130%, Near Average=90-110%, Below Average=70-89%, Much Below Average=Less than 70%.

CBRFC: Colorado Basin River Forecast Center.

Forecast Period: The period from April 1 through July 31, unless otherwise noted.

kaf: Thousand Acre-Feet. See Acre-Foot above.

Inflow: The volume of water that flows into a reservoir or lake.

Median: The middle value of an ordered set of values. Half of the values are higher and half of the values are lower. When the set contains an even number of values the median is the average of the two middle numbers.

NOAA: National Oceanic and Atomospheric Administration.

NWS: National Weather Service.

Water supply forecasts take into consideration present hydrometeorological conditions and use average basin temperatures and precipitation for the forecast period. As the forecast season progresses, a greater portion of the future hydrologic and climatic uncertainty becomes known and monthly forecasts become more accurate. For more information on the tools we use, consult Water Supply Forecasting Tools.

Volume forecasts represent adjusted flows; that is, observed flows with upstream water use taken into account. Adjusted flows will closely approximate natural or unimpaired flows. However, not all upstream diversions or impoundments are measured or quantifiable. For specific adjustments used with each forecast point, consult the Guide to Water Supply Forecasting.

The Water Supply Outlook is issued monthly January through May by the Colorado Basin River Forecast Center. It represents a coordinated effort between the National Weather Service, Natural Resources Conservation Service, Bureau of Reclamation, U.S. Geological Survey and local water district managers.

Note: Data used in this report are provisional and are subject to revision.

For more information, or to be included on the mailing list, please contact:

Colorado Basin River Forecast Center
2242 W North Temple
Salt Lake City, UT 84116
(801) 524-5130
www.cbrfc.noaa.gov